1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus with an improved structure of a driving frame, to which power transmission members are mounted, and a manufacturing method thereof.
2. Description of the Related Art
An image forming apparatus refers to an apparatus that prints an image on a printing medium according to an inputted image signal, and may be, e.g., a printer, a copying machine, a fax machine, a multi-function printer (that has multiple functions of printing, scanning, copying and faxing), or the like.
An image forming apparatus comprises a plurality of driven parts (hereinafter, referred to as “driven bodies”), such as, e.g., rollers, a photosensitive drum, a belt or the like, which may exhibit various movements necessary in carrying out various operations, e.g., conveying printing media or printing an image on the printing medium. The driven bodies are driven by a driving device.
The driving device may include a source of driving force, e.g., a motor, and power transmission members, which transmit the driving force from the driving source to the driven bodies. The power transmission members may include, e.g., gears, couplings and power regulation members.
Generally, the motor and the power transmission members are mounted on a metallic base plate to form a sub-assembled unit. The sub-assembled unit is mounted to an inner surface of the frame of the main body of the image forming apparatus, and transmits driving power to those components requiring motion.
On the base plate are provided a plurality of holes corresponding to mounting positions of the power transmission members, and metallic supporting shafts are fitted in the holes to rotatably support the power transmission members. In order to prevent the supporting shafts from rattling or being separated from the base plate, the metallic supporting shafts may typically be securely fixed to the base plate by caulking or press-fitting. An example of an image forming apparatus having supporting shafts (caulking shafts) secured to the base plate by caulking may be found in, e.g., Japanese Patent Laid-open Publication No. 2002-182540.
Unfortunately, however, the process of installing the supporting shafts in the corresponding holes in the base plate may not be the ideal assembly process in terms of the manufacturability and efficiency.
Further, in order to maintain the proper image quality, the arrangements of the supporting shafts, e.g., the relative distances between the supporting shafts, straightness of the supporting shafts, perpendicularity of the supporting shafts to the base plate, or the like should be ensured during the assembly process and/or maintained in operation. However, a conventional mechanical coupling of the supporting shafts to the base plate, e.g., through caulking or press-fitting, may be limited in ensuring and maintaining such proper arrangement of the shafts.